The present invention relates to a fast charging arrangement between a charger and a battery-powered device.
A rechargeable battery, for instance a Ni--Cd battery, is used especially in portable devices, such as radio-telephones, as the current source of the device. Such batteries must be regularly recharged, a discrete charger being commonly used for this purpose, among others in order to reduce the weight of the mobile or portable device maximally.
In known fast charging arrangements, a three-conductor connection is used between the charger and the device to be charged, the conductors being plus (current feed conductor), ground (return conductor) and the signal conductor for measuring the battery temperature. The temperature signal is used for controlling the charge current of the battery from fast charge to trickle current, when the temperature has reached a preset maximal value. The charging current may also be controlled in terms of the voltage, but the battery temperature has to be supervised in this case as well, the charging being impossible with a battery that is heated or cooled too much. The temperature and voltage control requires control circuits, which so far have been incorporated in the charger or in a charger-support assembly. For this reason, several conductors are required between the charging control logic and the battery to be charged. In prior art solutions, this has been resolved with a three-conductor connection between the charger and the battery-powered device. This is an expensive and in some cases even an impractical connection, given that the contacts needed are not particularly common.